I'm having the same issue with SSX 3. I went and bought a copy yesterday for about $12, only to find that its unplayable on the Xbox 360 due to random pauses every 30 seconds or so. Saving is also impossible...when it tries to save, I get a message saying that it can't save to the hard disk.
I thought maybe it was the disk, but when i tried it on my old xbox, it worked flawlessly.
I'm pretty sure I'm running the latest emu update. I downloaded something when I tried Halo 2 out for the first time.
Anyone else have this problem?